Process of dyeing with vat dyes



Patented Sept. 23, 1941 PROCESS OF DYEING WITH VAT DYES Jean G. Kern, East Aurora, N. Y., assignor to National Aniline & Chemical Company, Inc., New York, N. Y., a corporation of New York No Drawing. Application November 2a, 1938, Serial No. 242,743

f Claims.

This invention relates to the art of dyeing, and particularly to the art of dyeing cellulosic textile fibers, such as cotton. or regenerated cellulose fibersin the form of yarns or piece goods, with vat dyes.

As is well known, the vat dyes are insoluble in water in the unreduced form, but upon reduction with a reducing agent, such as sodium hydrosulfite, they are converted to leuco forms which are soluble to a certain extent in alkaline solutions. In dyeing with these dyes, the procedures used involve either first forming an alkaline solution or suspension of a leuco vat dye, contacting the material to be dyed with the solution or suspension, and then oxidizing the dye in the fabric, or applying'the unreduced vat dye to the material, subsequently passing the impregnated material through an alkaline solution containing a the material, and then oxidizing the dye.

At the present time, piece goods are generally dyed with vat dyes in any one of three methods involving the use of the above procedures. In the first two methods, a jigger and a padding machine are used, respectively. vThey are similar in that a non-acid solution or suspension of a leuco vat dye is employed, the piece goods being brought into contact with the solution or suspension so as to impregnate the material with the relatively soluble leuco vat dye. The dyeing is then completed by oxidizing the leuco dye in the goods, as by passing the goods through an oxidizing bath, and finishing in the usual manner. In the third method for dyeing piece goods with vat dyes, the goods are padded with a padding liquor containing an unreduced vat dye, water, and a thickener, and are then passed through an alkaline bath of hydrosulfite wherein the unreduced dye is converted to the leuco form in the presence of the goods. The dyeing of the piece goods is completed in a manner, in general, similar to that employed in dyeing piece goods in a reduced solution. Raw stock and spun cotton are generally dyed in dyeing machines in which these materials are brought into contact with a nonacid solution or suspension of a leuco vat dye. Dyeing of yarns is accomplished in a similar manner except that the solution or suspension of the leuco vat dye is passed'through the yarns dspcsed on perforated beams or the like.

' The reduced bath which is required in most of the above-described processes is ordinarily made by passing a water mix of the vat dyestufi' through a fine screen (e. g., 200 mesh per square inch) to form an aqueous paste, diluting the paste somewhat with water, and adding it to a dye bath containing a corresponding amount of alkali and a reducing agent such as sodium hydrosulfite. The dyeing is carried out by first raising the temperature of'the dye bath to a suitable point according to the particular dyestuff used and, when complete reduction of the dyestufl is efiected, starting the dyeing operation. It is important in order to secure satisfactory .results that during the dyeing operation the dye be kept in as complete solution or dispersion as possible. Although the theoretical considerations upon which the process of dyeing with vat dyes is based are not clearly understood, it is known that results, which are evidenced by the brilliancy, 1

penetration, fastness, and yield in the process, are better as the leuco vat dyes are more finely divided and more nearly in true solution.

In order to obtain a solution or fine dispersion of the leuco vat dyes in the dye hath, it is im-- portant first that the dyestuff as added to the dye bath be very finely divided. To this end the dyestuff, prior to being introduced into the dye bath, is converted to a finely-divided form and is ordinarily employed in the form of a paste prepared as described above by screening a mixture of the dyestuff and water. Pastes of this type may contain, in addition, dispersing agents and/or other suitable ingredients. The dyestufl may also be supplied in the form of a powder containing the finely-divided vat dyestufl and materials which assist in making the powder readily dispersible in water. Even with the use of the dyestuff pastes and powders at present in commercial use, some color value is often lost because the fiber does not absorb all of the dye present in the bath. This is due to the fact that part of the dye is not in a suitable adsorbable form. The unused and therefore wasted dyestufif in many cases adheres loosely to the surface of thefibers and is washed oiT readily during the soaping operation which follows the dyeing. Also, in many cases the production of even dyeings has been prevented because of the excessive amnity of the reduced dyestufi for the fiber, some portions of the fiber being dyed more readily than other portions.

r The present invention has for its principal object the provision of a process of dyeing with vat dyes whereby well-penetrated, brilliant, and level dyeings may be obtained.

Another object of the invention is to provide,

a process of dyeing with vat dyes characterized by the facts that the dyes are substantially comproduction of excellent results.

A further object of the invention is to provide novel dyeing liquors containing vat dyes which liquors are adapted for use in the production of valuable dyeings.

Other objects of the invention will inpartbe obvious and will in part appear hereinafter.

The present invention involves the use in dyeing with vat dyes of one or more hydroxylated polyamino alkyl ethers or thioethers. These ethers and thioethers are compounds which conta n a plurality of amino groups and at least one hydroxyl group. The central radical of these compounds is a radical containing two or more alkyl radicals linked together by oxygen or sulfur. The amino groups of these compounds may be unsubstituted or may contain alkyl radicals or aralkyl radicals as substituents. As employed in this specification and claims, the term alkyl radicals denotes and includes chain and cyclic alkyl radicals. The hydroxyl group or groups of the compounds may be in the central radical thereof or may be in an N-alkyl radical or radicals. Where the central aliphatic radical is free from hydroxyl groups, at least one and preferably two or more of the substituents of the amino groups are hydroxyalkyl radicals.

Thus, the hydroxylated polyamino alkyl ethers and thioethers which can be used in the vat dye compositions of the present invention may be represented by the general formula:

wherein R represents a radical consisting of alkyl radicals joined together by oxygen or sulfur- (which alkyl radicals may be open chain or cyclic alkyl radicals and which may be unsubstituted or may contain substituents which do not alter the essential characteristics of the compounds such as, for example, hydroxyl, alkoxy, and aralkyloxy groups, etc.); X1, X2, X3, and X4 each represents. hydrogen, an alkyl radical, an arallwl radical, or a hydroxyalkyl radical; and n represents a small whole number. In

cases where the radical represented by R is free from hydroxyl groups, at least one of X1, &, X3, and X4 represents a hydroxyalkyl radical. It is preferred to employ compounds in which the amino groups are substituted by at least one, and preferably two or more, hydroxyalkyl radicals regardless of whether the radical represented by R contains hydroxyl groups. p

' It will be understood that the substituents of the amino groups of these compounds may themselves contain, in addition to hydroxyl groups, substituents which do not deleteriously aflect the properties of the compounds; for example, they may contain substituted or unsubstituted alkoxy groups as substituents. In this connection it should be noted that where an N-aralkyi radical contains two ormore carbon atoms in the alkyl radical thereof, and this alkyl radical contains hydroxyl groups as substituents, it is regarded as a hydroxyalkyl radical for the purposes of this invention.

In particular instances one or another of the compounds of the above class will be somewhat preferable for use to others of the class. In general, for economic and technical reasons, those which are ordinarily preferred for use in the processes of the invention are hydroxylated polyamino alkyl ethers or alkyl thioethers in which the central radical contains two or more, especially two or three, ethylene groups. Further, the preferred compounds contain at least one, and preferably two or more, hydroxyethyl radicals as substituents in the amino groups.

The above-described hydroxylated polyamino alkyl ethers and thioethers are of low volatility and are easily soluble in water, alcohol, and in most organic solvents. The compounds which have low molecular weights have low melting points and are viscous liquids at ordinary temperatures; the viscosity of the compounds increasing with lncrease of their molecular weight. The compounds which have high molecular weights on the other hand are crystalline or amorphous solids which melt above 50 C. The hydroxylated polyamino alkyl ethers and thioethers, despite the presence therein of the oxygen and/or sulfur atoms, are strongly alkaline.

As examples of typical hydroxylated polyamino alkyl ethers and thioethers which are adapted for use in the vat dye compositions of the present invention, the following may be mentioned: I

di- (2' -ethanol-2-amino-ethyl-) ether omomam-omomon o I om0H,NH-c11,om011 di- (2' ,3 '-propandio1-2-amino-ethy1-) ether OH:CH:NH-CHaCHOHCHi0H di (gluco-2-amino -ethyl-) ether oH,cH,-NH-cH.(cH0H).oHioH CH (CHOH)4CHIOH bis- (di-N-2 -ethanol-2-amino-ethyl-) ether CHzCHzOH CHzCHr-N CHICHZOH CHICHflOH cmcm-N A cmomon bis- (dl-2',3'-propandiol-2-amino-ethy1-) ether orncnoncmon CHzCHa-N cannon-onion I cnlononcmon CIhCH -N CHICHOHCHZOH 2-amino-ethyl-) ether CHo(n) CHiCHr-N cincnonornofl C4Ho(n) emcee-N cmcnoncmon di- (ethanolamino-ethyl-) sulfide di(2',3'-propandiol-2-amino-ethyl-) sulfide CHzCHz-NHCH2CHOHCH2OH s CHiCHPNHCHICHOHCHlOH N-bi s- (diethanol-aminoethoxy-ethyl-) ethanolamine CHzCHzOH cmorn-o-omorn-N CH2C HaQH HO CHzCHz-N CHCHOH CHzCHr-O-CH:CHr-N omcmon di-N-4-cyclohexanol-2-amino-ethyl-) ether crn-cn, CBhCHz-NH-C CH-OH cm-crn o our-on,

CHzCHz-NH-C CH OH It has been found that the hydroxylated polyamino alkyl ethers or thioethers produce a number of valuable effects when they are added to vat dye baths for the dyeing of textile fibers, particularly natural and artificial cellulosic fibers. Thus it has been found that a dye bath consisting of a true solution of the leuco vat dye is obtained by mixingone or more of these hydroxylated polyamino alkyl ethers or thioethers with a finely-divided vat dye and water, and then introducing the resulting mixture into an aqueous solution containing corresponding amounts of alkali and a reducing agent, such as sodium A dye bath prepared in this way produces excellent results when used in dyeing textile fibers. Further, it has been found that i if the above-described alkyl ethers or thioethers are incorporated in a padding liquor containing an unreduced vat dye they have the dual effect of assisting in producing an effective dispersion,

of the insoluble dye in the padding liquor and of increasing the solubility of the leuco vat dye formed when the material impregnated with the,

padding liquor is passed through the jigger containing the alkaline solution of the reducing agent. The alkyl ethers and thioethers may also be added to the alkaline reducing solution in the jigger where they apparently act to increase the solubility of the leuco vat dyesin the impregnated material, their incorporation in this alkaline reducing solution being of advantage, re-

gardless of whether the alkyl ethers or thioethers have also been incorporated in the padding liquor.

The present invention can be practiced in several difierent ways. For xample, in dyeing with a non-acid solution of a leuco vat dye, as in a jigger dyeing machine or a yarn machine, the dye and the hydroxylated polyamino alkyl ether or thioether may be separately added to an alkaline solution of a reducing agent. However, for convenience, and because in this way rapid dispersion and corresponding rapid reduction of the vat dye is effected, it is preferred to add the alkyl ethers or thioethers to the dye bath in admixture with the vat dye in the form of a suspension. A

suspension of this type for use in the preparation.

of dye baths can be prepared by mixing the alkyl ethers or thioethers with a vat dyestufi paste comprising essentially a finely-divided unreduced vat dye and water. The resulting mixture is then diluted somewhat with water to form a suspension which is passed through a screen of the type referred to above. As a result. of this treatment a. highly dispersed suspension of the unreduced vat dye is obtained and the suspension is added to the dye bath containing the alkali and the reducing agent. on heating the dye bath to the temperature required at the beginning of the dyeing operation, complete reduction of the vat dy is effected and what appears to be a true solution of a leuco vat dye is, formed.

This solution or vat is adapted for use in the dyeing of piece goods in a jigger, or the dyeing of raw stock, spun rayon, or yarn in the machines ordinarily used for dyeing textile fibers in these forms. The dyeing operation is ordinarily completed in about 45 minutes. The material is then rinsed, treated with an oxidizing agent such as sodium bichromate or sodium perborate, rinsed, soaped, again rinsed, allowed to dry, and finished according to the usual methods.

Textile fibers can be dyed in accordance with the prescent invention using the pad and jig process by incorporating one or more. of the above-described hydroxylated polyamino alkyl ethers or thioethers in the padding liquor or in the development bath or both. border to obtain the full efiect of the alkyl ethers or thioethers, it is generally preferred to incorporate them in the padding liquor. Th padding liquor in accordance with the present invention can be prepared by mixing one or more of the hydroxylated polyamino alkyl ethers or thioethers with a finely-divided unreduced vat dyestufi", and

then adding to the resulting mixture water, a

gum, and an oil, such as bleaching oil, in suitable proportions so as to form a liquor having the desired concentration of ingredientsJIn using this liquor the material to be dyed is padded therewith, the padded material is dried, and the dyeing developed by working the impregnated material on a jigger in a solution containing the alkali and reducing agent. If necessary, additional dyestufi may be added in the jigger.

Instead of preparing a mixture for incorporation with the other ingredients of a vat or padding liquor as described above, there may be employed for the preparation of these dyeing solu-' tions or suspensions a vat dyestuff paste containing one or a mixture of the hydroxylated polyamino alkyl ethers or thioethers prepared, for example, as described in my application Serial No.

242,741 filed of even date herewith. Further, in place of the vat dyestuff pastes described above, there may be used vat dye powder compositions prepared as described in my United States Patents Nos. 2,067,926 and 2,074,150, in which case the dyestuif powders are first impasted with water and the resulting vat dyestuff pastes are then used in the same manner as the pastes of finelydivided vat dye and water, referred to above.

While the reason for the improvements resulting from the use of the above-described hydroxylated polyamino alkyl ethers or thioethers in dyeing processes in accordance with the present invention is not clearly understood, it appears that these improvements are due in part at least to the fact that these assistants are sufliciently basic to react with leuco vat dyes to form addition products which are more soluble than the leuco vat dyes themselves. Thus, while in the conventional vat it is usually the case that some of the leuco vat dye present therein is not completely dissolved, in a vat to which has been added one of these assistants the leuco vat dye is substantially all in solution. This result is surprising since these ethers and thioethers contain in their molecules th acidic ether oxygen and sulfur atoms. Because of the relatively high solubility of the hydroxylated polyamino alkyl ethers or thioethers, any reaction products formed between them and the leuco vat dyes are of increased solubility in water as compared with th leuco vat dyes themselevs.

The improvements resulting from the use of the hydroxylated polyamino alkyl ethers and thioethers in accordance with the present invention are varied. For example, their use results in improvement in the exhaust of vat dye baths, whereby dyed materials are obtained having an increased depth of shade as compared with the shades usually obtained. These assistants further act to equalize the depth of dyeing and give deeply penetrated and level results because of their property of retarding the rate of absorption of the dyes by the fiber. The penetration of the dyed material which results when proceeding in accordance with the present invention appears to be due in part to the wetting and penetrating powers of the alkyl ethers and thioethers for textile materials. This action is especially important when dyeing with chlorinated blues of the indanthrene type such as Carbanthrene Blue BCS (Color Index No. 1114).

On soaping a material dyed in accordance with the process of the present invention in a boiling soap solution, the dyestufl remains on the fiber, which thus retains the full color value of the penetrated dyestuif. As a feature of the invention it has been found that th present process is particularly important when used in the dyeing of shirting materials with the indanthrene class must be such as do not change in cast on repeated washings with soap. when dyeing shirting material with the various indanthrene blues, examples or which are Carbanthrene Blue GCD (Color Index No. 1113) and Carbanthrene Blue BCS (Color Index No. 1114), vivid and redcast shades are obtained at the end of the process which are stable and do not change on repeated washings.

When the hydroxylated polyamino alkyl ethers or thioethers are incorporated in the dyeing compositions by mixing them with a. dyestuff paste which is added to the dye bath, as is preferred practice, these assistants aid in insuring that the dyestufi is well-dispersed, thus expediting the screening operation which ordinarily precedes the incorporation of dyestufi paste into the dye bath. While this property of the assistants is of advantag in any case, it is particularly valuable when the pad and jig dyeing process is used; in this process it is of utmost importance to obtain uniform dispersion of the finely-divided dye.

The following examples will serve to illustrate the invention:

Example 1.An 8% per cent shade of Carbanthrene Blue GCD (Color Index No. 1113) on 150 pounds of mercerized cotton piece goods is obtained in the following manner. 12.75 pounds of Carbanthrene Blue GCD paste are mixed with 6 blues. The shades obtained on materials of this pounds of di-(gluco 2-amino-ethyl-)ether. To the resulting mixture 1 gallon of cold water is added and the suspension thus formed is passed through a fine screen. A speck-free paste is obtained which is added to a jigger dye bath containing 10 pounds of caustic soda, 15 pounds of sodium hydrosulfite (concentrated10 pounds being added immediately and the remaining 5 pounds after one passage), and gallons of water. The temperature is raised to F. and after complete reduction the dyeing is started at this temperature. The temperature is then allowed to rise to F. over a period of 30 minutes and the dyeing operation is carried on at this temperature for about 15 minutes. The goods are then given one wash, four passages in an aqueous solution containing 2 pounds of sodium perborate per 100 gallons at a temperature of 120 F., two cold washes, and five passages in a boiling soap solution containing 3 pounds of soap per 100 gallons; The goods are thereafter rinsed and washed in the open, dried, and finished in the usual manner.

Example 2.In this example an 8% per cent shade of Carbanthrene Blue GCD is obtained on pounds of mercerized cotton piece goods using a vat dyestufi paste prepared by mixing 400 parts .by weight of a press cake of Carbanthrene Blue GCD (containing '70 per cent water and 30 per cent solids as dry vat dye) with a smooth paste composed of 100 parts of water and 500 parts of di-(N-amyl N gluco 2 amino ethyl ether.

12.75 pounds of this vat dyestuff paste are screened and introduced into a bath consisting of 100 gallons bulk and containing 10 pounds of caustic soda (dry) and 15 pounds of sodium hydrosulfite. The dyeing process in this bath is carried out as described in Example 1.

Example 3.This example ofiers an illustration of the application of the present invention to the dyeing of the piece goods by the pad and jig method. In this example a vat dyestufl' paste prepared by mixing 1000 parts by weight of Carbanthrene Blue GCD aqueous paste containing 17 per cent totai dye solids and 1% per cent Leukanol with 500 parts by weight of bis-(di-N- 2'-ethanol-2-amino-ethyl-) ether and then evaplowing liquor:

to 1000 parts. The padding liquor is prepared by mixing pound of this vat dye color paste, 11 /2 gallons of water, 8 ounces of gum vtragacanth, and 5 pounds of bleaching oil, the whole making up 12 gallons bulk; This padding liquor is then used for padding cotton shirting cloth, the pressure of the pad roller being so regulated as to leave 60 per cent of moisture in the padded cloth. The padded material is then dried and developed in a jigger containing a developing bath prepared in the same manner as the dye bath of Example 2 prior to the addition of the vat dyestufi paste of that example, an additional quantity of the above vat dyetuff paste being added to the solution in the jigger so as to produce an 8 per cent dyeing. The oxidationand finishing of the material are carried out in the usual manner.

Example 4.This is another example of the application of the present invention to dyeing by the pad and jig method which difiers principally over the process described in the preceding example in that the assistant is added to the development bath rather than to the padding liquor. The padding liquid is composed of 5 pounds of Carbanthrene Blue GCD, 11 /2 gallons of water, 8 ounces of gum tragacanth, and 5 pounds of bleaching oil to make up a total of 12 gallons bulk.

The development bath is the same as that described in Example 3 except that a .quantlty of bis (di-2',3-propan-diol 2 amino-ethyl-) ether 'equal to the amount of dyestufi is added. The

dyeing is carried out in the same manner as in Example 3.

In place of the Carbanthrene Blue GCD of this example there may be employed an equal amount of Carbanthrene Dark Blue DR. (Color Index 1099) or Carbanthrene Violet 2R (Color Index 1104). i;

Example 5.-This is another example of the application of the present invention to dyeing by the pad and jig method where the assistant is added to the development bath. 150 pounds of rayon piece goods are padded through the fol- 12.75 pounds of Carbanthrene Blue GCD in the form of an aqueous paste containing 17.5 per cent dye solids, the rest being principally water, are diluted with 16 gallons of water to which 1 pound of gum tragacanth and pounds of bleaching oil have been added. The resulting suspension is agitated so as to form a stable emulsion and then is poured into the padding box of a padding machine. The pressure of the pad roller (squeeze roller) is so regulated as to leave 100 per cent of moisture in the padded cloth. The material is then dried and developed in the jig. The development bath in the jig is made up as follows: 10 pounds of caustic soda (dry) are dissolved in 5 gallons of water which are then poured into the jig tank. 10 pounds of sodium hydrosulfite (concentrated) are added thereto and immediately afterwards 5 gallons of an aqueous solution containing 12 pounds of bis-(til-a2-ethanol-2-amino-ethyl-) sulfide are introduced, and the total of the liquor in the jig is adjusted to 100 gallons. The temperature is raised to 110 to 115 F. and the dyeing is started at this temperature. After one 'passage an additional 5 pounds of sodium hydrosulfite (concentrated) are added to the bath and the temperature is allowed to rise to 125 'F. for about 30 minutes and the dyeing operation is continued for to 20 minutes longer at this temperature. The goods are then given one washing, four passages in sodium perborate (although this step may be omitted), two cold washings, and the material is finished as in the foregoing Example 1.

A uniform, brilliant blue dyeing is obtained showing no selvage, as is often obtained on rayon piece goods by present methods, with excellent penetration.

Example 6.This is an example of the applica-- the size and model of the machine used. The

a vat dyestufi paste already containing the hydroxylated polyamino alkyl ether or thioether in place of the vat dyestufi paste used above. In this case, the addition of a hydroxylated polyamino alkyl ether or thioether as such to the dye bath may be dispensed with.

The Carbanthrene Dark Blue DR of the above example may be replaced with other vat dyes; e. g., excellent resultsmay 'be obtained using Carbanthrene Violet 2B.

As previously indicated, the foregoing examples are merely illustrative of a few of the ways in which the present invention may be practiced. Hence, the procedures herein described may be varied widely within the scope of the invention. Thus, in place of the hydroxylated polyamino alkyl ethers and thioethers used in the processes described in the examples, there may be employed one or a mixture of the hydroxylated polyamino alkyl ethers and thioethers of the above class; e. g., there may be employed any one or a mixture of those specifically mentioned above. While the results obtained in particular cases will vary depending upon the specific ether or thioether used, in using any of the above class, the advantages herein pointed out can be obtained. With respect to the amount of hydroxylated polyamino alkyl ether and thioether required to produce these advantages, it will be recognized that this will be dependent upon the dyestuff employed, the material to be dyed, and

the specific dyeing procedure used. In this connection it is to be noted that the assistants not only act to increase the solubility of leuco vat dyes, but also appear to act upon textile fibers to increase their ability to absorb the dyes. In general, there should be employed an amount of hydroxylated polyamino alkyl ether and thioether about equal to the amount of dyestufi employed and ordinarily the amount of hydroxylated polyamino alkyl ether and thiother should not be reduced below about part by weight for each part by weight of the dyestuflf. Although an excess of an alkyl ether or thioether ordinarily does not have a critical efl'ect upon the operativeness of the process, the use of an excess is undesirable for economic reasons.

The process of the invention, in general, may be employed with advantage for dyeing with any vat dyestuff. Among suitable vat dyestuffs may be mentioned the following:

Color index' No. Carbanthrene Yellow G paste 1118 Carbanthrene Golden Orange 2RT paste 1097 Carbanthrene Golden Orange G Double paste 1096 Carbanthrene Blue Green FFB double paste- 1173 Carbanthrene Violet 2R paste 1104 Carbanthrene Dark Blue DR paste 1099 Carbanthrene Flavine GC double powder" 1095 Carbanthrene Red Violet 2RNX paste 1161 Carbanthrene Brilliant Green supra. 1101 Brilliant Indigo 4G 1189 from a dye bath, the improvement which comprises carrying out the dyeing with the aid of a polyamino compound of the following general wherein R. represents a radical consisting of lower alkyl groups joined together by a member selected from the group consisting of oxygen and sulfur; X1, X2, X1, and X4 each represents a member selected from the group consisting of hydrogen, alkyl radicals, aralkyl radicals, and hydroxyalkyl radicals, at least one of the substituents represented by X1, X2, A1, and X4 being a hydroxyalkyl radical when the radical represented by R is free from hydroxyl groups; and n represents a whole number notv greater than 2.

2. In the dyeing of textile fibers with vat dyes by a process in which the fibers are contacted with a non-acid solution of a leuco vat dye, the

improvement which comprises carrying out the dyeing with the air of a hydroxylated aliphatic diamine in which the central radical consists of lower alkyl radicals joined together by a member selected from the group consisting of oxygen and sulfur and containing as N-substituent at least one hydroxyalkyl radical, said diamine being free from N-substituents other than alkyl radicals, aralkyl radicals and their hydrom derivatives.

3. In the dyeing of textile fibers with vat dyes by the pad and jig process in which the fibers are impregnated with a padding liquor comprising a suspension of an unreduced vat dye and are then passed through a developing bath comprising an alkaline reducing solution, the improvement which comprises carrying out the process with the aid of a hydroxylated aliphatic diamine in which the central radical consists of lower alkyl radicals joined together by a member selected from the group consisting of oxygen and sulfur and containing as N-substituent at least one hydroxyalkyl radical, said diamine being free from N-substituents other than alkyl radicals, aralkyl radicals and their hydroxy derivatives.

4. The process of dyeing cellulosic textile fibers with vat dyes which comprises contacting the fibers with a bath comprising a non-acid solution of a leuco vat dye and for each part by weight of said leuco vat dye at least one-half part by weight of a hydroxylated aliphatic diamine in which the central radical consists of lower alkyl radicals joined together by a member selected from the group consisting of oxygen and sulfur and containing as N-substituent at least one hydroxyalkyl radical, said diamine being free from N-substituents other than alkyl radicals, aralkyl radicals and their hydroxy derivatives.

5. A vat dye bath comprising an alkaline solution of a leuco vat dye and for each part by weight of said leuco vat dye at least one-half part by weight of a hydroxylated aliphatic diamine in which the central radical consists of lower alkyl radicals joined together by a member selected from. the group consisting of oxygen and sulfur and containing as N-substituent at least one hydroxyalkyl radical, said diamine beim; free from N-substituents other than alkyl radicals, aralkyl radicals and their hydroxy derivatives. I

6. A padding liquor for dyeing with vat dyes comprising an aqueous suspension'of an unreduced vat dye, a thickener, and for each part by weight of said unreduced vat dye at least onehalf part by weight of a hydroxylated aliphatic diamine in which the central radical consists of lower alkyl radicals joined together by a member selected from the group consisting of oxygen and sulfur and containing as N-substituent at least onehydroxyalkyl radical, said diamine being free from N-substituents other than alkyl radicals, aralkyl radicals and their hydroxy derivatives.

7. A developing bath for developing unreduced vat dyes on piece goods comprising an aqueous solution containing caustic soda, sodium hydrofrom a dye bath, the improvement which comprises carrying out the dyeing with the aid of bis- (di-2' -ethanol-2-amino-ethyl-) sulfide.

10. In the dyeing of textile fiberswith vat dyes from a dye bath, the improvement which com- 

